Fix some shallow bugs in Demo/parser/unparse.py, and add tests:

- insert commas between entries in del statement
  - left and right shifts were represented as >> and << (respectively); reverse
  - unindent properly after for: else:  or while: else:
  - add parens around the result of an unary operation
  - add parens around negative numbers, to avoid turning (-1)**2 into -1**2.

Demo/parser/test_unparse.py

@@ -0,0 +1,61 @@
+import unittest
+from test import test_support
+
+import cStringIO
+import ast
+import _ast
+import unparse
+
+forelse = """\
+def f():
+    for x in range(10):
+        break
+    else:
+        y = 2
+    z = 3
+"""
+
+whileelse = """\
+def g():
+    while True:
+        break
+    else:
+        y = 2
+    z = 3
+"""
+
+class UnparseTestCase(unittest.TestCase):
+    # Tests for specific bugs found in earlier versions of unparse
+
+    def check_roundtrip(self, code1, filename="internal"):
+        ast1 = compile(code1, filename, "exec", _ast.PyCF_ONLY_AST)
+        unparse_buffer = cStringIO.StringIO()
+        unparse.Unparser(ast1, unparse_buffer)
+        code2 = unparse_buffer.getvalue()
+        ast2 = compile(code2, filename, "exec", _ast.PyCF_ONLY_AST)
+        self.assertEqual(ast.dump(ast1), ast.dump(ast2))
+
+    def test_del_statement(self):
+        self.check_roundtrip("del x, y, z")
+
+    def test_shifts(self):
+        self.check_roundtrip("45 << 2")
+        self.check_roundtrip("13 >> 7")
+
+    def test_for_else(self):
+        self.check_roundtrip(forelse)
+
+    def test_while_else(self):
+        self.check_roundtrip(forelse)
+
+    def test_unary_parens(self):
+        self.check_roundtrip("(-1)**7")
+        self.check_roundtrip("not True or False")
+        self.check_roundtrip("True or not False")
+
+
+def test_main():
+    test_support.run_unittest(UnparseTestCase)
+
+if __name__ == '__main__':
+    test_main()